{ "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "## CS 458: GBDM Chapter 4: Resources\n", "
\n", "\n", " " ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## Chapter Summary\n", "\n", "We discuss how resources affect the decision-making process. We elaborate a general definition of a resource as something that satisfies the enabling condition for a plan. We develop a taxonomy of fifteen types of resources and eight separate dimensions for classifying resources. In this context, we will discuss cognitive resources, such as memory and attention. Our model of goals leads us to a cognitive analysis of emotions and moods." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## 4.1 Goals, Plans, and Resources\n", "\n", "Goals, plans, and resources are closely associated. This basic triad is depicted in Figure 4.1. The following associations hold among goals, plans, and resources.\n", "\n", "- Goals give rise to plans. That is, plans provide a means for achieving goals. The goal of hunger may lead to the plan of going to a restaurant.\n", "\n", "- Plans give rise to goals. Plans often involve the instantiation of sub-goals. The plan of going to a restaurant may lead to the sub-goal of finding a taxi.\n", "\n", "- Plans require the use of resources. The execution of a plan may involve the use of a resource as a precondition. To take a cab, you need to have enough cash." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "- Resources give rise to plans. There may be a standard plan for the acquisition of a resource. If you need cash to pay for the cab, you may go to an automatic teller machine.\n", "\n", "- Resources give rise to goals. Unexpected resources can lead to opportunities — unanticipated goals. For example, while going to the automatic teller, you may notice an interesting restaurant and decide to abandon the goals of getting cash, taking a cab, and going to the other restaurant. The new restaurant is an opportunistic resource which allows goal substitution.\n", "\n", "We may use knowledge about the associations among goals, plans, and resources, as well as knowledge about the process of using resources to make inferences about goals." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## 4.2 Inferring Goals\n", "\n", "In a goal tree or similar hierarchical representation, goals are ranked according to importance. The more important a goal, the higher it would appear in the goal tree. An agent’s action might be explained as an attempt either to achieve or preserve some positive goal state or to block some negative goal state. Furthermore, when given a choice between multiple actions, an agent will usually choose that action which is in service of the most important or highest goal or collection of goals.\n", "\n", "Given the interdependence between goals and actions, one may often infer one from the other. Given knowledge of an agent’s goals and the choices of actions, one might well predict what action the agent will take, as in the following example.\n", "\n", "> Example 4.1 John was thirsty. He opened the refrigerator door.\n", "\n", "We infer that John will get something cold to drink.\n", "\n", "At the same time, by observing what choices an agent makes, one may then infer what goals the agent was trying to achieve.\n", "\n", "> Example 4.2 John opened the refrigerator door. He took out the milk and got an empty glass.\n", "\n", "We infer that John is thirsty.\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "The notion of the ranking or importance of goals can be given more explicitly by relying on two basic principles for the achievement of goals:\n", "\n", "> Principle 1 Resources are required to achieve goals.\n", "\n", "> Principle 2 Agents wish to maximize their achievement of goals.\n", "\n", "These principles are similar to Wilensky’s meta-themes [Wilensky, 1981]. A natural consequence of these two principles is that agents wish to maximize their resources. The concept of a resource can be more explicitly defined.\n", "\n", "> Definition 4.1 A resource is something that satisfies an enabling condition of one or more plans.\n", "\n", "We view resources quite generally. Any plan requires certain resources for its achievement. To succeed, an agent must possess these resources. He must have the wherewithal — the necessary means. For example, two common resources are time and money. Many (if not all) goals require some expenditure of time. The absence of resources can prevent the achievement of goals:\n", "\n", "> Example 4.3 John wanted to go to the movies, but he was broke.\n", "\n", "> Example 4.4 John wanted to go to the movies, but he had to work late.\n", "\n", "The fact that resources have to be expended in achieving goals clearly constrains the choices that a planner must make.\n", "\n", "It is also possible in many cases to measure the resources spent in the achievement of a goal. Given the corollary of maximizing resources, we may derive our original principle of importance for inferring goals." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "> Principle of Importance. The importance of a goal is proportional to the resources that the agent is willing to expend in pursuit of that goal, and vice versa.\n", "\n", "Just as the very ranking of goals is subjective, so is the value of resources, as shown in the next examples.\n", "\n", "> Example 4.5 John spent $100,000 (his life savings) running for governor.\n", "\n", "> Example 4.6 Nelson spent $10,000,000 (his annual income) running for governor.\n", "\n", "These examples demonstrate that resources should not be measured on an absolute scale, but rather viewed subjectively relative to the agent concerned.\n", "\n", "We should also point out that the calculation of importance from resources must take into account resources already allocated to a given goal. For example, an agent may expend lots of time or money in pursuit of a goal while still not achieving the intended goal. The importance of that goal at that time is not measured merely by the incremental cost of achieving the goal, but rather should take into account the cumulative resources expended. \n", "\n", "> Example 4.7 John had worked his way through college and law school. To get enough money to take the bar review course, he would have to sell his car.\n", "\n", "The decision for John is not simply whether passing the bar exam is worth losing his car. If John does not pass the exam, he has in effect lost the time, money and effort spent on his legal education. John has invested in his education, which has increased its importance. John must protect that investment." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "> Principle of Investment. The importance of an active goal is proportional to the resources that the agent has already expended in pursuit of that goal.\n", "\n", "We use the term active to indicate that this principle should not apply to latent or pending goals. Still, there is a sense in which we clearly believe current goals to be more important than goals that are not being pursued.\n", "\n", "However, there are times when one must abandon an investment. The sayings “do not throw good money after bad” or “cut your losses” refer to this situation. Just because a goal is important does not mean that you will achieve it. A less important goal will be abandoned more readily than an important goal. Thus, it will be harder to abandon a high investment goal, than a goal of low investment.\n", "\n", "The principle of investment is descriptive, not prescriptive. Economists argue that true investment decisions should consider only future costs and returns. Past expenditures should be considered “sunk costs” and not affect the decision. We suggest, however, that the principle of investment is a psychological reality which influences decision making. This model is consistent with Prospect Theory of Tversky and Kahneman (1979) which is discussed in chapter 8. [Note: economic decision theory stipulates that an agent\n", "should ignore Sunk Costs. However, Tversky and Kahnemann, as always, project psychological \n", "evidence and justification.]" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "## 4.3 Types of Resources\n", "\n", "Given the specific definition of a resource as something that satisfies the enabling conditions of other goals, there are numerous things that would qualify as resources. Here are examples.\n", "\n", "### Time\n", "\n", "> Example 4.8 John was often late for work.\n", "\n", "We wish to distinguish three different aspects of time as a planning resource. First, there is time as an amount — the duration of time required for completion of a task. For example, it might take John 15 minutes to drive to work, 20 minutes to take the bus, or 45 minutes to walk.\n", "\n", "Second, there is the required completion time — a deadline for finishing a task. This resource reflects the urgency of a task. For example, we might assume that John is supposed to be at work at 9 am. Thus, if he drives, he can leave home at 8:45.\n", "\n", "Finally, there is the need to synchronize actions — the timing of an action. For example, if John plans to take the bus and leaves home at 8:40, he may still be late if the bus leaves on the half hour.\n", "\n", "By comparing time to other resources, we do not mean to suggest that reasoning about time is simple. AI researchers have demonstrated many subtle and difficult problems associated with temporal reasoning [Allen, 1984, Dean, 1985, Shoham, 1986, Hanks, 1990]. On the contrary, we wish to suggest that reasoning about other resources, such as the ones listed below, will also be complex.\n", "\n", "We also want to emphasize that time exhibits many features found in resources in general. Time can satisfy enabling conditions on plans.\n", "\n", "> Example 4.9 John had enough time to eat lunch before his meeting.\n", "\n", "Time limitations can lead to problems that may result in changes in plans.\n", "\n", "> Example 4.10 John did not have enough time to eat at Chez Che, so he got a burger instead.\n", "\n", "A surplus of time can provide a new opportunistic goal.\n", "\n", "> Example 4.11 John’s meeting was canceled, so he decided to take a walk.\n", "\n", "Time is no doubt different from other types of resources in many ways. However, we feel justified in treating time as a resource just the same." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Money\n", "\n", "> Example 4.12 John bought a new car.\n", "\n", "Money, like time, is of no intrinsic value. Money’s value lies in the fact that it can be exchanged for other resources that will satisfy goals. Furthermore, since most goals can be translated into a cost in terms of money, money can provide a convenient means for comparing the value or importance of otherwise disparate goals.\n", "\n", "As with time, we recognize that money has many complex and difficult aspects. The fields of economics, accounting, and finance examine many of the subtle and intricate features of money." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Senses and Physical Abilities\n", "\n", "> Example 4.13 John stopped the car when he saw the man with the white cane.\n", "\n", "Sight, speech, hearing, touch, and the use of limbs are all resources that people rely on for a vast number of actions. The lack of one of these abilities is an infirmity which restricts the plans or goals that one may pursue. Someone who is afflicted may resort to substitutes, such as hearing aids or prosthesis. Some physical abilities, such as strength, have a quantitative measure, e.g., “John can lift 300 pounds.”" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Skills\n", "\n", "> Example 4.14 John needed a ride to work since he did not know how to drive.\n", "\n", "Certain plans require skills. Possession of a skill is a resource needed for pursuing certain plans. Physical skills include typing, handwriting, playing the piano, and sports. Mental skills would include reading, math, and language fluency." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Credentials and Consent\n", "\n", "> Example 4.15 John needed a ride to work since his license had been revoked.\n", "\n", "Society often requires an explicit statement of qualifications or franchise. Suffrage, citizenship, and professional degrees are examples of this type of resource. More generally, an agent may require permission from an authority to perform some action. A parent may forbid a child to watch television.\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Place and Proximity\n", "\n", "> Example 4.16 John did not need a ride to work since he lived only two blocks from the office.\n", "\n", "Many plans require that an agent be in a specific physical location. Therefore, once the agent is in that location, he has satisfied an enabling condition for the plan. In the present example, we can see that John has solved his commuting problem by moving closer to work. The phrase “being in the right place at the right time” captures this notion of location (and time) as a resource. Many plans are described by the initial change in location, e.g., “going to the movies” or “going to a restaurant.”" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Space and Volume\n", "\n", "> Example 4.17 John could not find a parking place near the office.\n", "\n", "Being in the right place is not always sufficient. Many plans require a certain physical volume to be occupied by people or objects. Consider an efficiency apartment versus a three bedroom house, or a motorcycle versus a station wagon. It is easier to park a motorcycle, but you can carry more in a station wagon. Physical space and volume can be considerations in many types of plans." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Relationships\n", "\n", "> Example 4.18 John’s brother gave him a ride to work.\n", "\n", "People can help other people. Someone can act on your behalf as your agent. In chapter 5 we will discuss how relationships can be viewed as resources.\n", "\n" ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Health\n", "\n", "> Example 4.19 John was too sick to go to work.\n", "\n", "Life is the ultimate individual resource. You do not leave home without it. Almost all goals that a person pursues requires a pulse. Different levels of illness will limit plans accordingly." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Functional Objects\n", "\n", "> Example 4.20 John needed a ride to work while his car was in the shop.\n", "\n", "We have many tools for achieving disparate goals. Some of the tools give rise to goals of their own. Complex tools have a teleological character. We speak of a car needing gas and oil. We understand that the common design and function of an automobile require us to service its needs. If we viewed our car merely as an immobile sculpture, we would have fewer things to take care of." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Knowledge and Facts\n", "\n", "> Example 4.21 John got lost on his way to his new job.\n", "\n", "Knowledge is different from a mental skill. In this example, John knows how to drive and how to follow directions. He simply does not have accurate directions. He is missing the correct plan." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Natural Resources\n", "\n", "> Example 4.22 John grew some vegetables in his back yard.\n", "\n", "This is the common notion of resources found in nature. Natural resources would include minerals, lumber, food, coal, oil, clean air, clean water, harbors, and fertile soil." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "### Power\n", "\n", "> Example 4.23 John called the mayor to get the potholes fixed.\n", "\n", "Position or rank or office provides certain authority. The mayor can order the city street department to fix the potholes. Similarly, if the mayor is indebted to John for any reason, John can effectively order the mayor. That is power. In the following chapter on interpersonal relationships, we discuss the process of persuasion, one component of which is the power relationship between agents.\n", "\n", "We do not suggest that the preceding list is exhaustive. It is merely illustrative. The reason for viewing this disparate collection of conditions all as resources is to provide a uniform way of dealing with them to infer the importance of goals." ] }, { "cell_type": "markdown", "metadata": {}, "source": [ "\n", "
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